This invention relates to improvements in the security of input data to digital computers. More particularly, it relates to a personal data entry stylus which simultaneously enters data into a computer system and transmits a security code which identifies the user and may optionally log the user on to the computer system.
In data processing systems, a central processor executes a sequence of program instructions in response to data supplied by an input device and displays the results of those program instructions to an output display device. A visual display device such as a scanned cathode ray tube display, a gas panel display, an array of light emitting diodes, a liquid crystal display panel, or other types of visual devices may be used to display the output from the computer system. While an alphanumeric text is frequently utilized as an output, a graphical representation of the data has been recognized as a powerful means for characterizing data. Frequently, the results displayed on the visual display device by the computer system will require the user to input additional data to the computer system. Human factor studies have shown that where the user can input data directly on the visual display screen itself, the greatest immediacy and accuracy between man and machine is achieved.
Various types of interactive input devices for use at the display surface have been provided in the prior art. One of the first devices was the light pen, which is an optical detector in a hand held stylus, which is placed against the face of a cathode ray tube. The location of the light pen is determined by detecting the coordinates of the dot of light which is the scanning raster of the display. A second interactive input device is a opaque graphic tablet, upon which a sheet of drawing paper might be placed for tracing with a stylus or other instrument. A horizontal wire grid and a vertical wire grid are embedded in the surface of the tablet which are driven with an electromagnetic signal. The computer system establishes the stylus position by receiving the grid signal through the stylus by way of a signal detector.
Yet another type of input device in the prior art is a mechanical deformation membrane which is placed over the display screen. The membrane is a transparent overlay which consists of two transparent conductor planes disposed on a flexible surface so that when the user mechanically displaces one of the conductor planes to touch the other by a finger or stylus touch, the conductors are brought into electrical contact with each other. Appropriate electronics and software are provided to translate the electrical signals generated by the finger or stylus touch to the position on the visual display.
However, the ease with which a user can input data into a computer system with these interactive input devices, also creates concerns about terminal and computer system security. One prior art security method describes a personal identification card which has an encoded combination of punched holes in it. The user places the card over a designated area on the CRT display screen and then places a light pen over the holes in the card while it is pressed against the the face of the display. The information registered by the light pen through the holes in the card will provide a security password to the computer system, thereby validating the user of the card as a legitimate user of the terminal. While this method addresses security at log-on, it does not provide security where a system is continuously in use by multiple users and no log-on and log-off procedures are followed. In addition, it is somewhat cumbersome to use both a card and light pen in conjunction with the display to provide the security password.
Other methods for providing security of a computer terminal such as standard identification numbers and passwords, as well as the use of a credit card device and reader have been used in the prior art. All of these methods and systems address the security of a system at log-on. In some situations, for example, at a hospital nurses station, it may be desirable to leave a system continuously running without the need for log-on/log-off procedures, yet maintain security so that only legitimate users may access the terminal. It would also be desirable to automatically identify the user of the terminal so that the data entered at the terminal may be associated with a particular user.